No, don’t assume. Ask the stepmom.
Being a stepmom is different from being a Mom. So I tell stepmoms, slow your roll and adjust your expectations. But dads need to adjust their expectations, too. If a dad assumes his kids will embrace her as Mom, he expects too much and that leads to conflict. So dad: cherish her as your wife and give her Mom-like respect in front of your kids. Ask her if she’s comfortable with a particular role or parenting task. Don’t assume and play to her strengths so everyone wins.